1. Field of the Invention
The present invention relates to a collision safety control device, and in particular to a ground or earth wiring structure of the collision safety control device controlling actions of a collision safety equipment such as an SRS (Supplement Restraint System) airbag or a seat belt pretensioner etc.
2. Description of the Related Art
Prior art ground wiring structure of such a collision safety control device takes advantage of a cab 1 and a frame 2 in a cab over engine truck as shown in FIG. 5, in which the collision safety control device (ECU) 3 is connected to a combination switch 4 and a driver's seat airbag 5 with harness portions H1 and H2, and is further connected to a driver's seat pretensioner 6 with a harness portion H3 connected to the harness portion H1.
Also, the collision safety control device 3 is connected to a ground portion 7 secured to the frame 2 on the right side of the vehicle body (driver's seat) through the harness portion H1 and a harness portion H4 connected to the harness portion H1, where the ground portion 7 is secured to the frame 2 by a bolt and a nut.
It is to be noted that the harness portion H1 is further connected to a warning meter 18 as well as a battery terminal 9 through a harness portion H5. Another battery terminal 10 is connected to a battery ground (frame earth) 11, and that the above harness portions H1-H5 can be formed of a single harness, including therein both of a signal line from the collision safety control device 3 and a power supply line from the battery terminals 9 and 10.
The above collision safety control device 3 is activated by a power supply voltage (+24V) from the battery terminal 9, in which a sensor (not shown) reacts when the vehicle body collides with an object, so that the collision safety control device 3 responsive to an output signal of the sensor sends a drive signal to the driver's seat airbag 5 (and a front passenger's seat airbag not shown), thereby inflating the airbag immediately. Also, the collision safety control device 3 drives the driver's seat pretensioner 6 (and a front passenger's seat pretensioner not shown) when there is a high possibility of rear-end collision. The warning meter 18 is an alarm lamp for the airbag 5 or the driver's seat pretensioner 6.
There has been proposed an airbag device for automobile which houses an airbag and an inflator inside a steering wheel, in which a mechanical sensor having a weight or a bias pin made of a magnet is housed within a pad of the steering wheel, a coil is arranged around the outer periphery of a pad portion to effect a magnetic field of a coil onto the weight or the bias pin and to project a firing pin (see, e.g. Japanese patent application publication No. 7-196004).
On the other hand, there has been proposed an electrical circuit protective device which comprises a first case having a vehicle mounting portion secured to the vehicle body; a second case sectioning a storage chamber with the first case; a substrate arranged in the storage chamber and having an electrical circuit; and a connector electrically connecting the electrical circuit to external equipments, wherein the first case is made of resin, and a ground conductive path is formed of a grounding member between the substrate and the vehicle body (see, e.g. Japanese patent application publication No. 2003-260992).    [Patent Document 1] Japanese Patent Application Publication No. 7-196004    [Patent Document 2] Japanese Patent Application Publication No. 2003-260992
The prior art shown in FIG. 5 has a problem that if the harness portion H1 or H4 from the collision safety control device 3 to the ground portion 7 is disconnected at a time of offset collision etc, the collision safety control device 3 will not operate the driver's seat airbag 5.
While there is a conventional system ensuring a ground wiring redundancy by arranging a unit case of the collision safety control device 3 so as to contact with the cab 1, this system causes an incomplete contact part to arise between the unit case and the cab 1, or the cab 1 and the frame 2, so that a complete ground wiring could not be made. Also, with such an incomplete ground wiring, a controller inside the unit case can be damaged by a lightning strike.